Means for voltage regulation by aid of an exciter



Dec. 11, 1956 u. LAMM 2,774,031

MEANS FOR VOLTAGE REGULATION BY AID OF AN EXCITER Filed June 21, 1954Inventor UnoLamm United States PatetttO MEANS FOR VOLTAGE REGULATION BYAll) or AN EXCITER 1 Uno Lamm, Ludvika, Sweden, assignor to AllmannaSvenska Eiektriska Aktiebolaget, Vasteras, Sweden, a corporation ofSweden Application June 21, 1954, Serial No. 438,178

Claims priority, application SwedenJune 22, 1953 6 Claims. (Cl. 322-79)In the automatic regulation of a main machine utilizing an exciter it isusual to allow the exciter to magnetize itself in a manner normal for D.C. machines, so that it gives a suitable basic voltage without anyoutside measures being taken. Usually a shunt winding is necessary forthis purpose. Further a co acting or counteracting magnetizationcomponent is supplied from a regu lator, e. g. through a controlwinding, whereby the voltage of the exciter can be controlled in a waydetermined by the regulator.

In known regulating arrangements operating according to this principle,there is usually the risk that the polarity of the exciter becomesreversed. This can arise when during regulation the counter-actingexcitation component derived from the regulator becomes so large and canact for such a length of time that the flux of the exciter changes itsdirection. When this happens, the action of the regulator becomesreversed, i. e. instead of resetting the voltage of the generator to adesired value, this will increase, so that the voltage will increase toan undesired value.

The present invention relates to means for controlling the excitation ofa main machine by means of an exciter provided both with a shunt windingand a control winding, wherein the shunt winding is series connectedwith a uni-directional valve or with a combination of unidirectionalvalves and wherein the control winding in series with a regulator isseries connected with the same uni-directional valve or combination ofsaid valves.

In the accompanying drawing Figs. lshow some forms of execution of theinvention.

In Fig. 1, 1 designates the armature of an exciter. This has a shuntWinding 2, where is series connected with a uni-directional valve 3. Theuni-directional valve is so directed that it allows the current to passthrough the shunt winding from the positive pole of the exciter to itsnegative pole. The uni-directional valve can be of the dry valve type,but any other type of valve can be used, c. g. an ionic valve or amechanical valve, i. e. a relay which is opened it the current throughits main contacts tends to change its direction.

One end of the control winding 5 is connected to a point 4 between theshunt winding 2 and the uni-directional valve 3. The valve 3 is seriesconnected with the current circuit formed by the control winding 5 andthe regulator 6. The regulator can be of any type, for instance atransductor regulator or a tube regulator. '{t can also be a rotatingmachine, e. g. a methadyne, the magnetization of which is controlled bythe magnitude to be regulated.

The unidirectional valve 3 will be traversed by the dififerentialcurrent between the current through the shunt winding and that throughthe control winding. If the control winding is co-acting, these currentswill be added, but if the control winding is counter-acting, theuni-directional valve will block, when the current through the controlwinding tends to exceed the current through ice 2 the shunt winding.When the unidirectionalvalve blocks the current in this way the windings2 and 5 will act as series connected windings, the'same' current beingforced mfisw in both of them. When the number of turns of the windingsis made equal, the resulting magnet'omo'tive foicefherof will be zero,so that the reversal of polarity is avoided.

in certain cases it is possible that the remanence in the magneticcircuit of the exciter may be lost, when the magnetomotive' force of thewindings is zero. Both windings can, in spite of their equalsize, givedifferent magnetomotive forces, so that the resulting magnetomotiveforce will be somewhat negative, whereby the risk of demagnetization isincreased. Such an eventuality can be prevented by deliberately givingthe shunt winding 2 a somewhat larger number of turns than the controlwinding 5. By this measure the voltage is also taken up more quicklyafter the above described operation has taken place. I

If the shunt winding and the control winding have the same number ofturns, it may be suitable to connect, as

shown in Fig. 2, an impedance, e. g. a resistance 7, in parallel withthe control winding 5. Part of the current from the regulator will thenflow through this resistance, and this ensures that the magnetomotiveforce from the shunt winding 2 prevails over the magnetomotive forcefrom the control winding 5, when the valve 3 blocks.

Fig. 3 shows a modification of the arrangement according to Fig. l. Theuni-directional valve according to this form is arranged as a two-pulsetwo-way bridge connection 8, those two terminals of the bridge 8, whichare D. C. terminals when the connection is used as a rectifier, areconnected in series with the shunt winding 2, and the other twoterminals of the bridge are connected in series with the control winding5.

If the control current in the opposite direction tends to exceed thecurrent through the shunt winding 2, the upper left hand and the lowerright hand valve elements will block, whilst the two remaining valveelements allow the coupling of the shunt winding and the control windingso that the same current will flow through these windings.

Fig. 4 shows a development of the arrangement according to Fig. 1. Theuni-directional valve of the last mentioned arrangement is replaced by abridge connection 9 of valve elements in two-pulse-two-way-connection,the D. C. terminals of which belong to a common current path for theshunt winding and the control winding. The A. C. terminals of the bridgeconnection are connected to an A. C. source at the terminals 10, fromwhich a current can be taken which gives the exciter a basicmagnetization, which can aid in preventing its demagnetization and whichalso can be used for accelerating the taking up of the voltage after theprocedure with blocked uni-directional valves has taken place.

It is of course not necessary to use quite unsymmetrical uni-directionalvalves, i. e. valves which allow the current to pass in a certaindirection and block it in the opposite direction. Within the scope ofthe invention it is for instance possible to use a non-linear inductanceelement as shown in Fig. 5 in a connection according to Fig. 1. As avalve an inductance coil is used with an iron core, which gives a largeinductance when it is nonsaturated but a small inductance when it issaturated. With the current flowing in the normal direction the ironcore will be kept saturated, but if the current tends to Change itsdirection, the magnetization of the core must be reversed, which, if thecore is sufiiciently dimensioned, will take such a long time that it, inreality, means that the change of current is prevented, because theexciter then succeeds in taking up voltage in the 3 proper direction,before the current has time to change its direction. This means that thenon-linear inductance has the same purpose as a valve element.

I claim as my invention:

1. Means for controlling the magnetization of a main machine, comprisingan exciter provided with two excitation windings one of which isconnected as a shunt winding to the brushes of said exciter,uni-directional valve means series connected with said shunt winding,and a regulator for controlling the excitation of said exciter, saidregulator and the second excitation winding being connected in serieswith said valve means.

2. Means according to claim 1, in which said valve means is arranged asa rectifier bridge connection so that those terminals of the connectionwhich are direct current terminals when the bridge is used as arectifier, are con-- nected in series with the shunt winding, and thetwo other terminals of the bridge are connected in series with thesecond excitation winding and the regulator.

machine, comprising an exciter provided with two ex citation windingsone of which is connected as a shunt winding to the brushes of saidexciter, non-linear inductance means series connected with said shuntwinding, and a regulator for controlling the excitation of said exciter,said regulator and the second excitation winding being connected inseries with said inductance means.

References Cited in the file of this patent UNITED STATES PATENTS1,966,558 OHagan July 17, 1934 FOREIGN PATENTS 360,740 Germany June 11,192i

